1. Technical Field
The present invention relates to a conduction structure, a method of manufacturing a conduction structure, a droplet ejecting head, and a printing apparatus.
2. Related Art
A printing apparatus including a droplet ejecting head is used when printing is performed on a recording medium such as printing paper (for example, see JP-A-2006-289943).
The droplet ejecting head disclosed in JP-A-2006-289943 includes a flow channel forming substrate in which a pressure generating chamber that temporarily stores ink and an ejection port that communicates with the pressure generating chamber and ejects ink in the pressure generating chamber as droplets are formed, and a reservoir forming substrate which is provided on the flow channel forming substrate, and in which a portion of a reservoir that preliminarily maintains ink to be supplied to the pressure generating chamber is formed. Also, a piezoelectric element adjacent to the pressure generating chamber is arranged. The piezoelectric element is electrically connected to a driver IC that controls the driving of the piezoelectric element via a wiring pattern (conduction structure). Also, it is possible to securely eject ink droplets from the ejection port by driving the piezoelectric element.
Here, the piezoelectric element is provided in a space called a piezoelectric element maintaining portion provided on the flow channel forming substrate. Also, the wiring pattern connecting the piezoelectric element and the driver IC is constructed along the inclination surface provided on the flow channel forming substrate. The wiring pattern (conduction structure) connecting between the piezoelectric element and the driver IC is formed by various methods. For example, JP-A-2006-289943 employs a method of bonding the reservoir forming substrate and the driver IC while the position of electric wiring constructed on the inclination surface and the mounting surface of the driver IC and positions of connection terminals of the driver IC are matched, and then depositing plating metal on electric wiring on both the reservoir forming substrate side and connection terminals on the driver IC side by an electroless plating method. Then, the electric wiring of the reservoir forming substrate and the connection terminal of the driver IC are electrically bonded by depositing plating metal on both until the both are bonded each other.
Meanwhile, JP-A-2005-311122 and JP-A-2006-140247 disclose a method of arranging the semiconductor device on the wiring substrate and electrically connecting the wiring substrate and the semiconductor device by growing plating metal from both the connection terminal of the wiring substrate and the connection terminal of the semiconductor device by the electroless plating method.
However, in the method disclosed in JP-A-2006-289943, the electric wiring constructed on the mounting surface of the driver IC in the reservoir forming substrate and the connection terminal of the driver IC are maintained in a state of facing each other, and then are subjected to an electroless plating method. Therefore, the method of mounting the driver IC is limited to a so-called face down method. As a result, in the mounting of the driver IC, it is necessary to prepare a flat surface for face down mounting, that is, a surface corresponding to the mounting surface of the driver IC described above. Therefore, it is necessary to secure a wide mounting surface, and thus the line length of the wiring pattern becomes long. Accordingly, it becomes difficult to sufficiently increase the arrangement density of the electric wiring.
Meanwhile, in the method disclosed in JP-A-2005-311122 and JP-A-2006-140247, electric connection is obtained by using plating metal isotropically grown by an electroless plating method in the state in which the connection terminal of the wiring substrate and the connection terminal of the semiconductor device are separated from each other, and joining plating metal between the connection terminals separated from each other.
Since the plating metal isotropically grows as described above, when the plating metal is grown so as to join the connection terminals separated from each other, the plating metal widely expands at the same time in the width direction of the wiring pattern which is formed by plating (direction orthogonal to direction in which connection terminals to be joined are connected). Therefore, in order to prevent an unintended short circuiting, the adjacent connection terminals in the wiring substrate, or the adjacent connection terminals in the semiconductor device have to be separated from each other. As a result, the arrangement density of the connection terminals cannot be sufficiently increased, and it is difficult to reduce the size of the wiring substrate or the semiconductor device.